Using Lego Digital Designer and Blender
According to the Lego Digitial Designer manual it allows to export LXF, LXFML and LDraw files.


  Export. Export lets you create LXF, LXFML and LDraw files that can be
  opened in other applications


There are community developed Blender add-ons such as ImportLDraw by Toby Nelson that allow to import these models.